1. Easier really is better
The easier something is to do (i.e., the less mental and physical effort required from the perspective of the user), the more likely the user is to do it. Psychologists study these as “channel factors,” behavioral economists talk about using “nudges” to overcome the small frictions blocking action, and BJ Fogg argues strongly for simplicity—but the lesson is the same. We like to have some challenge in our lives, but we still “usually) take the easy route, all else being equal.

2. Familiar really is better
We’re just more comfortable with things we’ve seen before and actions that we’ve taken before. Again, there are lots of reasons—because of the “mere exposure effect” , or because we’ve built up skill and a sense of self-efficacy (a belief in our ability to successfully tackle the task)—but the lesson is the same. We take the familiar route, all else being equal.

3. Beauty really is better
We’re more comfortable with things (including products) that are easy on the eyes, shall we say. In part, it’s because of the “halo effect” —if we really like one aspect of something, we tend to like it overall. In part, it’s because our minds fundamentally mix the ease of viewing, the ease of remembering, and the ease of using something with the value we ascribe to it. Either way, we like stuff that looks good. Not avant garde and incomprehensible, but good.

4. Rewarding experiences really do make us want to come back
Our routines are often built around the expectation of a reward we’ve received in the[…]” “costs and benefits of action. Either way, conscious or not, we like rewarding experiences (i.e., you must have a good product that provides value to the user).

5. We really don’t want to fail
We avoid activity that we think we’ll be unsuccessful at. If we think we’ll fail, we foresee two problems—we won’t get the reward for completing the action, and we’ll feel stupid (or be judged harshly by our peers, fail to meet our commitments, etc.). So, another obvious point that bears repeating: don’t make people fail (frequently), or even make them expect that they’ll fail. A challenging experience can be good, but failure is bad.

6. We do urgent things first
If your toddler is about to touch a hot stove, and the college savings account you’ve set up for him is underfunded, which one will you act on first? Urgency matters. It’s so obvious that we often forget about it when we build our products—we assume that people have nothing else going on in their lives.

There are always exceptions, and that’s why we test out products in the field to see what is working and what isn’t. But these are six useful rules of thumb.